How many types of bees can you name? The answer most of you might come up with is honey, or bumble bee. But did you know there are 20,000 species around the world?

We rely on the common bees to carry out most of the world's pollination, but with their numbers dwindling - experts at Reading University say we now need to attract some of the other species to carry out the role - but how?

It's estimated a third of the food we eat is pollinated by bees - and we're not just talking honey. Their role is so important in our food chain that their contribution is worth £650 million to our economy. But experts are warning we need to act now to ensure that continues.

As bees transport pollen from flower to colony they accidentally pollinate all sorts of fruit and vegetables, which end up on our plates. But despite having 200 species here in the UK - only a couple pollinate our crops. Experts say we need to ensure other types are pollinating too, by making the right food and nesting resources available - whether on farmland, or in towns and cities. Ecologists at Reading University have compared it to a game of football.

"You might have all your stars playing on the field currently but you need to have a very strong squad on the bench so if your key player were unable to play for some reason you would need a good substitute to take up that role and that's exactly why we need to focus our efforts on conserving all the bee species that are available to us, and not just focus on the ones that are pollinating crops now."

– Deepa Senapathi, Ecologist, Reading University

Bees are worth £650 to our economy by pollinating the food we eat

The bees we rely on to pollinate crops for us now may not be around in the future because of changes in the climate, or a change in crops that grow on farmland. The University of Reading campus is a green space - full of flowers and plants. And that's what scientists are encouraging - that our urban spots have plenty of parks and gardens, or even balconies, where the right flowers and plants will attract different types of bees.

Deepa Senapathi is encouraging more species to pollinate our crops

"Pollination services in the UK are valued at £650 million per year and that was a figure from three years ago so that figure is only likely to go up so in terms of the econmomic services they provide bees are really important so you wouldn't want the economy to be hit we wouldn't be able to have the good quality strawberries and apples that we enjoy now so it impacts quality of life in very basic ways."

Researchers at Sussex University are calling on the public to help study why the number of bees is falling. Bees play a vital role in our countryside, pollinating fruit and vegetables. But many native species are declining rapidly. Now, it's hoped that "citizen science" will provide more clues about why the insects are under threat. Malcolm Shaw reports.